A.G.
Well I kinda think you might want to do it in private with her or on the phone a day or two before she comes over. Just because even though she will be happy for you it will no doubt upset her too. She might have a harder time handling the news in front of people. I am pregnant with my 3rd and my sister right now can't have any more kids (she has 2 the same age as my other 2) so I new it would upset her. And it did. So I told her over the phone a few weeks before I was going to see her. She acted happy for me...well kinda but after I got off the phone with her she called my Mom and cried. I guess she was pretty upset but by the time I saw her she was fine and over it. Now she is happy for me and is excited for me. So I would just tell her straight out and tell her you understand if she is upset. Once the shock is over with she will be ok and happy for you.